In data storage technology, a volume manager will group a collection of physical storage disks into one or more logical volumes, so that a user application will view each logical volume as a single storage device, even though the logical volume may contain multiple physical storage disks. Physical storage disks are also referred to as physical volumes. Volume managers that manage current storage hardware include, for example, the HP-UX LVM (Logical Volume Manager) which is commercially available from HEWLETT-PACKARD COMPANY, Palo Alto, Calif. and the LINUX LVM2 volume manager, as well as other volume managers from other vendors. A volume manager will manage the group of disks in the logical volumes by the use of configuration data which is data that the volume manager will store in a meta-data region in each physical storage disk belonging to the logical volumes. The meta-data region is used by the volume manager to manage the storage in the logical volumes and maintain how the user data maps to the physical storage disks.
Current volume managers are limited in the amount of user data that they can represent due to the outdated fixed physical size of existing disk resident metadata structures. Many current volume managers are designed with fixed disk layouts and fixed size data structures that were based on the storage size expectations that were acceptable in past years. As data storage needs continue to increase exponentially, these existing static data structures for meta-data are inadequate to keep up with current data storage needs. In other words, if customers will add new disks to the logical volumes, the user data will also increase in size and will have to be stored in the limited meta-data regions in the disks. Furthermore, disk sizes are also being increased in order to meet the increasing data storage needs, and typically, this trend disadvantageously leads to larger-sized devices.
Current data storage systems are not able to increase the amount of user data storage to an existing collection of disks, while using the limited disk regions already reserved for meta-data and also avoiding relocation (migration) or re-layout of existing user data. For example, in one current approach to attempt to store more user data, the storage system will migrate the user data to a new set of storage devices which has a larger space reserved up-front for meta-data structures. The disadvantages of this approach are that 1) customers need to have a second set of storage on hand; 2) the time to migrate may be quite large given today's database/file system sizes; and 3) it reserves larger disk space which is then not available for customer use. As another example, in another current approach to attempt to store more user data, the volume manager will store its meta-data on disk in a new modified data layout where the meta-data is split into different non-contiguous regions in the disks. Therefore, this approach disadvantageously requires a major restructuring to the software and to the migration of the user data to this new layout, and this layout of non-contiguous regions leads to maintenance difficulties for customers. Furthermore, if an existing disk is full, there would be no disk space to fragment the meta-data, unless the user data is moved to other disks, and this move of the user data leads to further disadvantages. Therefore, the current technology is limited in its capabilities and suffers from at least the above constraints and deficiencies.